The mass to charge ratio of an isotope was found to be $2.0 \times 10^{-7}$ kilograms per coulomb. If the charge on the isotope is $1.6 \times 10^{-19}$ coulombs, what is the mass of the isotope? HINT: Determine the ratio and cross multiply as usual.

The following substances are acids or bases. The ions they form in solution are shown:

$$\begin{array}{|c|c|c|} \hline \text { Substance } & \text { Acid/base } & \text { lons in solution } \\ \hline \mathrm{HCl} & \text { Acid } & \mathrm{H}^{+} \mathrm{Cl}^{-} \\ \hline \mathrm{HNO}_3 & \text { Acid } & \mathrm{H}^{+} \mathrm{NO}_3^{-} \\ \hline \mathrm{CH}_3 \mathrm{COOH} & \text { Acid } & \mathrm{H}^{+} \mathrm{CH}_3 \mathrm{COO}^{-} \\ \hline \mathrm{NaOH} & \text { Base } & \mathrm{Na}+\mathrm{OH}^{-} \\ \hline \mathrm{KOH} & \text { Base } & \mathrm{K}_{+} \mathrm{OH}^{-} \\ \hline \mathrm{NH}_3 & \text { Base } & \mathrm{NH}_4{ }^{+} \mathrm{OH}^{-} \\ \hline \end{array}$$

(a) What ion(s) do the acids have in common?

(b) What ion(s) do the bases have in common?

Consider the two acids $\mathrm{HCl}$ and $\mathrm{CH}_3 \mathrm{COOH}$. When in (separate) solutions they react in the following way:

• The $\mathrm{pH}$ of the $\mathrm{HCl}$ was measured at 1. The $\mathrm{pH}$ of the $\mathrm{CH}_3 \mathrm{COOH}$ was measured at $2.88$.
• $25 \mathrm{~mL} 0.1 \mathrm{~mol} / \mathrm{L}$ of each acid was reacted with an excess of sodium carbonate $\left(\mathrm{Na}_2 \mathrm{CO}_3\right)$. The reaction between $\mathrm{HCl}$ and $\mathrm{Na}_2 \mathrm{CO}_3$ was vigorous. The reaction between $\mathrm{CH}_3 \mathrm{COOH}$ and $\mathrm{Na}_2 \mathrm{CO}_3$ was much slower.
• Each reaction produced the same amount of $\mathrm{CO}_2$ gas.

(a) Which acid has the greatest concentration of $\mathrm{H}^{+}$ions in solution?

(b) Explain why the same amount of $\mathrm{CO}_2$ gas was produced despite the $\mathrm{pH}$ of the acids being different:

(a) Under what conditions would the first reaction be carried out in order to produce the greatest amount of hydrogen?

(b) To increase the hydrogen produced, the hydrogen is constantly removed from the system. How would this help produce more hydrogen?

Fresh water has a density of $1000 \mathrm{~kg} / \mathrm{m}^3$. Will the following objects sink or float if placed in it?

(a) A cork (density $=240 \mathrm{~kg} / \mathrm{m}^3$ ):

(b) A piece of lead (density $=11,340 \mathrm{~kg} / \mathrm{m}^3$ ):

Why is a compromise of 200 atmospheres and 400C used in the production of ammonia?

(a) Explain why the pressure in a sealed container of gas increases when heat is added to the system:

(b) Explain why the pressure in a sealed container of gas decreases when the system is cooled:

Discuss potential sources of error during a volumetric analysis with your lab partners (from making the standard solution to performing the titration). Name them and describe how you would minimize them. Use more paper if you need to:

The bicarbonate buffer system in the blood is a system evolved to reduce the change in the blood's $\mathrm{pH}$. The system is based around the bicarbonate ion $\left(\mathrm{HCO}_3{ }^{-}\right)$. The equilibrium is: $\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \rightleftharpoons \mathrm{H}_2 \mathrm{CO}_3 \rightleftharpoons \mathrm{HCO}_3{ }^{-}+\mathrm{H}^{+}$.

(a) What would be the effect of adding an acid $\left(\mathrm{H}^{+}\right)$to the system?

(b) How does adding the acid affect the blood's $\mathrm{pH}$ ?

(c) How is any acid added to the system ultimately removed? Explain your answer:

Calculating a $95 \%$ confidence interval $(95 \% \mathrm{Cl})$ provides a good estimate of how close the sample mean is to the true mean. The mean $\pm$ the $95 \%$ $\mathrm{Cl}$ gives the $95 \%$ confidence limits. On average, 95 times out of 100 , the true population mean will lie within the confidence limits. The $95 \% \mathrm{Cl}$ can be plotted onto graphs to determine significance. If they overlap there is no significant difference between the data. The $95 \% \mathrm{Cl}$ for student $\mathrm{A}$ is $1.27$ and for student $\mathrm{B}$ is $2.37$ at $\mathrm{p}=0.05$.

(a) Plot the mean dispensing volume and $95 \% \mathrm{Cl}$ for both sets of data on the grid right). Plot as a column graph with error bars.

(b) Is the difference significant? Why or why not?

Imagine a beaker half full of water (below right). The beaker is sealed with cling wrap. Some of the water will evaporate to form gaseous $\mathrm{H}_2 \mathrm{O}$. At some point the rate of gas forming will equal the rate of condensation.

(a) What might happen to the rate of gas forming if the beaker is warmed by placing it in the sun, or on a heat pad?

(b) How might this affect the amount gas in the system compared to the liquid water?

(c) The beaker is placed in a fridge. What would happen to the rate of gas formation now?

(d) How would this affect the amount of gaseous water compared to liquid water in the system?

Ammonia $\left(\mathrm{NH}_3\right)$ is a compound with $1: 3$ ratio of nitrogen to hydrogen atoms.

(a) If a sample of ammonia contains 1500 nitrogen atoms, determine the number of hydrogen atoms present?

A solution of NaOH is made up to 0.25 mol/ L. Calculate its pH:

(a) Use the calculated statistics for each data set to comment on how pipette size affected the dispensing accuracy:

(b) Set A has a lower standard deviation than set B. What does this tell us about the reliability of the data?

(c) How could you use this information to select the appropriate equipment for your experiments?